Moss has long been regarded as unusual among land plants for its resilience and apparent independence from fungal partnerships, which are common in other species. However, new research from UC Riverside indicates that this view may not apply in desert environments.

An Unexpected Partnership

More than 85% of land plants form relationships with fungi that exchange soil nutrients for sugars, and approximately 75% of these plants specifically associate with arbuscular mycorrhizal fungi, or AMF, which require a host to survive. Moss was considered the exception. All 10,000 known species were believed to exist without such fungal partnerships.

“That’s been the model,” said Jason Stajich, a UCR professor of microbiology and plant pathology and co-author of the study, published in New Phytologist. Mosses, he explained, simply didn’t need fungi. Recent findings now challenge that assumption.

Chasing Moss Through 100-Degree Heat

To investigate this, UCR doctoral researcher Kian Kelly collected samples from the Mojave and Sonoran deserts, focusing on biological soil crusts. These crusts contain complex communities of fungi, bacteria, algae, moss, and microscopic animals that stabilize desert soils. The team wanted to know whether desert mosses host different fungal communities than mosses in milder environments. “Sometimes I couldn’t find the same species of moss,” Kelly said of the search.

The team then processed moss samples and sequenced their DNA in the laboratory. They identified fungal genetic material, including AMF, which are typically unable to survive without a host plant. Furthermore, the fungal species present in desert moss differed from those found in moss from less extreme climates and from fungi in the surrounding soil. “We suspect that certain fungi are more helpful for surviving hotter, drier climates,” Kelly noted.

This mismatch made simpler explanations, such as contamination or fungi decomposing dead tissue, less likely. The evidence suggested a more specific association.

Unexpected Structures Inside Moss

Since DNA evidence alone could not confirm that fungi were living within moss tissue, Kelly stained samples with a dye that binds specifically to fungal cells and examined them under a microscope. He observed branching structures located inside the moss. “As soon as I saw that, I knew we had something really interesting,” Kelly said.

The structures resembled arbuscules, small, tree-shaped structures that fungi typically form within plant roots to facilitate nutrient exchange. Since moss lacks traditional roots, these structures were observed in the moss leaves. The researchers therefore refer to them as “arbuscule-like” rather than identifying them as true arbuscules. Whether nutrient exchange actually occurs between fungus and moss remains unconfirmed and will be the subject of future investigation.

Potential Implications

If this relationship is confirmed, its significance extends beyond desert ecology. Mosses belong to one of the oldest surviving lineages of land plants, which first colonized terrestrial environments approximately 470 million years ago. A fungal partnership present in moss tissue today could represent a remnant of the original alliance that enabled plants to adapt to life on land.

There are also more immediate implications. Biological soil crusts are fragile, and even small disturbances can take decades to heal. These ecosystems are increasingly threatened by rising temperatures and human activity. If fungi help desert moss survive heat and drought, understanding this relationship could guide future efforts to restore degraded soil crusts rather than merely documenting their decline. For now, the main conclusion is that moss, once thought to be independent of fungal associations, may have been getting help the entire time.

“The desert is full of things people overlook. Sometimes, the biggest surprises are the ones growing quietly beneath our feet,” Kelly concludes.

Austin Burgess is a writer and researcher with a background in sales, marketing, and data analytics. He holds an MBA, a Bachelor of Science in Business Administration, and a data analytics certification. His work focuses on breaking scientific developments, with an emphasis on emerging biology, cognitive neuroscience, and archaeological discoveries.